Pier eee es Te 
The Summer Birds of Shetland. 69 
the hollows and tunnels of the huge grass-tussocks covering 
the summit of the stack. Most of them contained four eggs, 
a good deal incubated. The nests were usually well con- 
cealed, as one would certainly think would be necessary, 
placed as they are in the centre almost of a colony of several 
hundred gulls—JZ. marinus and ZL. fuscus, neither of which 
species is at all averse to an ege-diet. No male eiders were 
seen on the top of the stack, but in the sea below and on the 
opposite coast of Papa about fifty were observed. The only 
other locality where this bird is at all abundant is Linga, off 
Whalsay. 
51. Black Guillemot (Uria grylle)—A somewhat extensive 
colony of U. grylle exists at the “ Horse of Burravoe,” in Yell, 
probably amounting to between forty and fifty pairs. While 
visiting that locality on the 18th June, every little “geo” we 
pulled into was enlivened and ornamented by the presence 
of these elegant little birds. 
55. Shag (Phalacrocorax cristatus)—One of the most 
extensive “shaggeries”” in Shetland is that upon the “ Horse 
of Burravoe,’ and many of the nests are easily accessible 
from aboat. I could have collected half a hundredweight of 
their eggs without much difficulty. No shag’s nest seen by 
me here or anywhere else in Shetland contained more than 
three eggs or young birds. 
58. Black-headed Gull (Larus ridibundus).—I have never 
met with this gull in Shetland, but I am aware of one or two 
localities where a few pairs nest. It is by far the rarest gull 
in the islands. 
63. Great Black-backed Gull (Larus marinus)—A colony 
of these grand birds, only second in size to that upon the 
inaccessible Holm of Noss, exists on the summit of the Lyra 
Skerry. I estimated this colony at about twenty-seven pairs, 
and counted ten of their nests in a line along the highest edge 
of the stack, besides others in different places. The estimate 
given in my former paper of the numbers of this gull on 
Noss is much too high,—there are probably less than fifty 
pairs this year. 
64. Great Skua (Stercorarius catarrhactes)—On the occa- 
sion of my first visit to Shetland in 1884, I heard reports of 
